The present invention relates to pre-collation copying systems, and more particularly, to a duplex copying system which provides pre-collated duplex copy sheet sets.
When multiple copies are made from a multi-page set of original documents, the multi-page copies thereof are usually separated into separate copy sets in proper order, which is known as collation. For example, for ten copies of a five page document set, the copies should end up in ten separate copy sets, each copy set having one copy of pages 1 through 5 therein, in that order. For duplex copies, which require two of the document pages to be copied on opposite sides of the same copy sheet, copying with collation is more difficult. Once the copies are collated into copy sets they can then be stapled, bound, or otherwise finished. Such a copy set may be a copy of a multiple page memo, report, brief, magazine, book, etc.
The collation of multiple copy sets is known to be performable manually or automatically, in two general ways. In one way, which may be called "post-collation" the original document pages need only be handled once per copy. All of the desired number of copies are made in one copying operation from each document page. The copies thus come out of the reproducer in un-collated form, e.g., ten copies of page one together, followed by ten copies of page two, etc. The post-collation can then be provided in a number of well-known ways by mechanical sorters or collators, which separate the copy pages into separate copy set bins. Each copy set of a given document page must be individually placed in a separate bin. Then the copy of the next document page must be placed adjacent the preceding copy page in each bin until the complete set is completed in each bin.
The conventional post-collation process has a number of disadvantages. It requires considerable mechanical handling of the copy sheets, with consequent potential jams and copy sheet losses. The sorters or collators required considerable space, weight, and expense in order to provide a sufficiently large capacity. A conventional sorter or collator had a limited maximum capacity for the number of copy sets, equal only to the number of its bins. Thus, a single 20-bin sorter can only collate for 20 copies of a document set and additional copies would be uncollated unless recopying, with document recirculation, is provided, or unless "limitless" sorting is provided by switching between two or more bin sets and unloading one set of bins while the other sets is being filled. Also, the maximum size of the copy sets including the maximum number of copy sheets which can be in each copy set, is limited by the size of the individual bins.
The use of sorters or collators can be completely avoided by "pre-collation", a different way of performing output collation. In pre-collation the originals are serially recirculated, and one copy made per page per recirculation, by the number of times corresponding to the number of copies desired. Thus, the copy sheets come out of the reproducing apparatus individually, but already in pre-collated order, i.e., to immediately form sets. Thus, for the exemplary ten copies of a five-page book, one copy at a time would be made of each document page in this order: pages 1, 2, 3, 4, 5; 1, 2, 3, 4, 5, etc., repeated a total of ten times to make ten copy sets. However, for bi-directional pre-collation copying, to which the present invention could be related the copying sequence would be 1, 2, 3, 4, 5; 5, 4, 3, 2, 1; 1, 2, 3, 4, 5, etc., i.e. the copying of the document set is switched between forward and reverse serial order.
In pre-collation copying, all copies may be collated in one or two large output trays rather than in multiple bins. A relatively simple offsetting or staggering device may be provided for the output tray, if desired, to displace each copy set slightly from the next for set recognition and separate removal, e.g., U.S. Pat. No. 3,630,607 issued Dec. 28, 1971, to H. Korn et al.
In pre-collation copying, as in U.S. Pat. No. 3,963,345 to D. Stemmle and M. Silverberg which is incorporated herein by reference, there is no limit on the number of copy sets. Operator unloading of each set is not required. The size of each copy set is limited only by the document page capacity of the document recirculation system, i. e. the maximum document set size. Completed sets can be removed from the output tray while the others are being produced. A complete first set is produced from the first copies, and is immediately usable for proofing. On-line finishing can be provided in which each copy set is bound while the next set is being produced. Binding of the pages in each set can be by stapling, sticking, glueing, etc.
The embodiment disclosed herein utilizes a preferred pre-collation system in which document recirculation for multiple serial copying is provided while retaining document sheets on an elongated web wound in document retaining storage scrolls for minimizing document handling and maximizing document protection, where the web is wound and unwound between these document retaining scrolls for the pre-collation document copying. However, it will be appreciated that other pre-collation copying systems may also be utilized in the present invention, and therfore, it is not limited thereto. Examples of other bi-directional document movement copying systems which are included herein by reference are disclosed, for example, in U.S. Pat. No. 3,574,459, issued Apr. 13, 1971, to K. Hartwig and in U.S. patent application, Ser. No. 552,003, filed Feb. 24, 1975, by D. O. Kingsland, now U.S. Pat. No. 4,008,958, issued Feb. 22, 1977. Also, an optical system for scanning during reciprocal motion is disclosed in U.S. patent application filed Feb. 24, 1975, Ser. No.: 552,004, by Daniel S. Hoffman now U.S. Pat. No. 3,994,588, issued Nov. 30, 1976.
The concept of fully manual pre-collation copying is well-known, in which an operator sequentially manually makes single copies of the pages of the document set and re-copies the set by the number of copy sets desired. Some examples of previously known automatic pre-collation copying systems for document sheets are disclosed in U.S. Pat. No. 2,822,172, filed Feb. 4, 1958, by C. R. Mayo et al., German Pat. No. 1,128,295, Oct. 25, 1962, by H. Rankers; and U.S. Pat. Nos. 3,499,710, by L. W. Sahley, 3,536,320, by D. R. Derby, and 3,799,537, by H. W. Karp. In the latter, the documents are recirculated in individual carriers.
The present invention is directed to duplex copiers, i.e., copiers capable of copying on both sides or faces of a copy sheet as opposed to only single side or simplex copying. This has obvious advantages in savings in paper or other copy media. Duplexing may be carried out manually by re-stacking the copy sheets after copying on the first side, and then placing them in a sheet feeder supply tray for copying on the second side, or preferably it may be carried out automatically by, for example, the use of an auxiliary or duplex feeder tray such as in the Xerox "4000" copier in which all of the copies to be duplexed are copied on one side and are all stored and then fed out for copying of the second sides thereof. Some examples of duplex copying systems are disclosed in U.S. Pat. Nos. 3,615,129; 3,645,615; 3,841,754; 3,844,653; and the references cited therein. It will be appreciated that documents being duplex copied may themselves be either simplex or duplex, although the document handling required may differ. Thus, for simplex documents the odd and even documents pages are on alternate separate documents. In contrast, for duplex documents even document pages occur on opposite sides of the same document, so that duplex documents may be arranged with all even pages in adjacent order or all odd pages in adjacent order.
One of the problems which occurs with reproducing machines when they do both simplexing and duplexing is the generation of improperly collated sets of copy sheets in the output tray. For simplex unidirectional copying proper collation can be obtained by properly orienting an output path and output tray so that if sheets 1 through 10 are copied serially in the forward order, 1 through 10, they will appear face down in the output tray in that order. Numerous sorter/collator type devices have been devised which are capable at a simplex mode of operation of providing properly collated sets of copies. However, when one performs duplex copying from serially ordered simplex originals 1 through 10, the resultant copies appear in the output tray in the page order 2, 1; 4, 3; 6, 5; etc. Proper collation in this instance requires an inverter.
Examples of selectable simplex-duplex sorter/collators for maintaining collation are disclosed in U.S. Pat. No. 3,750,880 issued Aug. 7, 1973, to P. Petrovsky, et al.; 3,866,904, issued Feb. 18, 1975, to D. J. Stemmle; and 3,833,911, issued Sept. 3, 1974 to J. R. Caldwell and D. J. Stemmle. For bi-directional pre-collation copying the copy output sets may be handled as taught in U.S. Pat. No. 3,977,263 issued Dec. 14, 1976. The sheet deflector or inverter structures shown in these references may be incorporated herein as alternative embodiments of structures for providing the face-up versus face-down output selections for the present invention.
Exemplary embodiments of the present invention are shown and described hereinbelow as incorporated into otherwise conventional exemplary xerographic apparatus and processes. Accordingly, said xerographic apparatus and processes themselves will not be described in detail herein, since various printed publications, patents and publicly used machines are available which teach details thereof to those skilled in the art. This includes the use of flat platen scanning optics systems for copiers. Some examples of such optics systems are disclosed in U.S. Pats. Nos. 3,775,008, issued Nov. 27, 1973, and 3,832,057, issued Aug. 27, 1974, and in their cited references. Structures and teachings from these and all of the other references cited herein may be incorporated by reference in the specification, to the extent appropriate.
One object of the instant invention that follows from the foregoing is the accomplishment of duplex copying in a pre-collation copier.
It is a further object of the present invention to increase the effective overall copying rate and effectiveness of duplex copiers.
Another object of this invention is to reduce the number of document recirculations in collation duplex copying systems in order to achieve a certain number of sets.
It is yet another object of this invention to reduce duplex tray capacity requirements of present duplex copying systems and to otherwise improve automatic duplex copying systems.
A further object of this invention is to allow unlimited duplex copying from a document set.
A still further object of this invention is to provide an improved automatic duplex system which requires only one photoreceptor and one transfer of an image instead of two separate photoreceptor drums or belts and two separate transfers of an image.
Yet another object of this invention is to provide duplex copying without requiring the use of an inverter.
The foregoing and other objects of the present invention are accomplished by interleaving a buffer set of copy sheets with the regular set of copy sheets. The buffer set contains, e. g., sheets having the even numbered pages of a document on one side and the blank or unused side of these sheets being fed to the copier to receive, for example, the images of odd numbered pages in the document. Thereby, collated sets of copies containing images on both sides in logical order are obtained. The input document is the equivalent of a simplex document having pages arranged numerically.